Optical disc

ABSTRACT

An optical disc includes a read-only area having a first wobble, which is a data wobble formed in the read-only area for only reading, a readable/writable area having a second wobble, which is different from the data wobble, and a connection area between the read-only area and the readable/writable area having a third wobble having the same frequency as one of the first and second wobbles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of Application Ser. No. 10/259,802,filed Sep. 30, 2002, now pending, which claims priority from KoreanPatent Application Nos. 2001-61042 and 2001-68633, filed Sep. 29, 2001,and Nov. 5, 2001, respectively, in the Korean Intellectual Propertyoffice, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disc which data is writtenon, read from, and deleted from, and more particularly, to an opticaldisc having a data wobble in a read-only area for only reading andanother wobble, which is different from the data wobble, in areadable/writable area, and having a connection area between theread-only area and the readable/writable area.

2. Description of the Related Art

In general, optical discs, such as DVD-RAMs, DVD-RWs, DVD+RWs, andDVD-Rs, which data is written on, deleted from, and read from, have beenused or proposed. In a case of these optical discs, data only forreading (read-only data), e.g., identification and serial number of theoptical disc, a version number of a format book, and a writing strategy,is written in an inner portion of the optical disc in a form ofunchangeable pits. A readable/writable area where data can be writtento, read from and deleted from, follows a read-only area for onlyreading to which the read-only data regarding the optical disc iswritten in the form of the pits. Further, a connection zone is formed tobe a physical interface between the read-only area and thereadable/writable area.

Japanese Patent Publication No. 1993-258469, as shown in FIG. 1,discloses an optical disc having a mirror area 100 formed between an Aarea 103, which is only readable, and a B area 105, which can bereadable and recordable, to maintain constant angular velocity forobtaining regular data density. The mirror area 100 has wobbling pitswp1 and wp2 containing tracking information at a head of each segment SGbut does not contain control information such as address.

A DVD-RAM shown in FIG. 2 includes the connection zone between theread-only area and a recordable area in a lead-in area, and theconnection zone is formed of the mirror area having no data within apredetermined radius of the optical disc. The mirror area is required toobtain a time margin to master a wobble and header pits with two beamsafter mastering the pits, which are the read-only data, with one beamduring a manufacturing process of the optical disc. The mirror area alsoprovides a drive with information about a starting point of therecordable area following the read-only area.

FIG. 3 is a view of a connection zone applied to a format of a 4.7 GBDVD-RAM. In detail, the connection zone is formed between a read-onlydata zone for only reading, in which data is written as embossedcharacters, and a recordable data zone. On the other hand, a DVD+RW, aDVD-RW, or a DVD-R does not have such a connection zone. Instead of theconnection zone in the DVD-RAM of FIG. 3, as shown in FIG. 4, a bufferarea 115 is formed at a border between a lead-in area 110 and a dataarea 120 using address information such as a wobble or a land pre-pit(LPP).

As mentioned above, the prior art establishes the connection zone onlywhen the read-only data is written in the form of the pits. However, ina case that the read-only data is written in the form of the pits andthe recordable area is written in the form of groups, it is difficult toobtain good-quality groove characteristics due to differentmanufacturing conditions of the pits and the grooves. Further, in ahigh-density and high-capacity disc having multi-recording layers, anoptical power loss occurs due to dispersion of a write beam when thewrite beam is illuminated on a pit area. To solve these problems, it issuggested that the read-only data be written in the form of a groovewobble having grooves with wobbles. However, the use of the groovewobble of different specifications, e.g., frequency, amplitude, trackpitch, or phase, in both the read-only area and the readable/writablearea, may cause errors due to the wobbles of different specification,e.g., a crosstalk of the wobble at an interface between the read-onlyarea and the readable/writable area. Accordingly, the connection zone isrequired between the read-only area and the readable/writable area whenthe read-only data is written as the groove wobble, not as the pit.

SUMMARY OF THE INVENTION

To solve the above and other problems, it is an object of the presentinvention to provide an optical disc in which read-only data for onlyreading is written as a first wobble in a read-only area for onlyreading and a second wobble, which is different from the first wobble,is written in a readable/writable area. The optical disc includes aconnection zone between the read-only area for only reading and thereadable/writable area, thereby enabling reliable reading/writingoperations of a reading and writing apparatus.

It is another object of the present invention to provide an optical discincluding an area containing data regarding an ending portion of aread-only area for only reading, thereby enabling efficient reading andwriting operations of a reading and writing apparatus.

Additional objects and advantageous of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

To achieve the above and other objects, there is provided an opticaldisc which data is written on and/or read from. The optical discincluding a read-only area for only reading having a first wobble, areadable/writable area having a second wobble that is different from thefirst wobble, and a connection area formed between the read-only areafor only reading and the readable/writable area.

The first wobble has a high frequency (first frequency), and the secondwobble has a low frequency (second frequency) lower than that of thefirst wobble.

The connection area includes a third wobble whose frequency decreasesgradually so that the entire frequency can be smoothly reduced from thehigh frequency of the first wobble to the low frequency of the secondwobble.

A first physical address of the readable/writable area is disposed nextto a last physical address of the read-only area.

The first wobble is a saw-toothed wobble.

The connection area is a mirror area.

The third wobble in the connection area is different from the first andsecond wobbles. Tracks of the read-only area, the connection area, andthe readable/writable area have the same track pitch.

The connection area includes at least one track. The read-only areaincludes a header field containing address data, and thereadable/writable area includes a wobbled groove containing addressdata.

The header field is disposed at a beginning or end portion of errorcorrection code (ECC) write units, or at a border between the ECC writeunits.

The first wobble in the header field has the same low frequency as thesecond wobble in the readable/writable area.

The optical disc further includes at least one recording layer.

The first frequency of the first wobble is expressed as a function ofthe second frequency of the second wobble by ƒ_(HF)=nƒ_(LF), where n isa positive integer, and f_(HF) and f_(LF) denote the first and secondfrequencies of the first wobble and the second wobble, respectively.

To achieve the above and other objects, there is provided an opticaldisc that includes a lead-in area, a lead-out area, and a data area,which is disposed between the lead-in area and the lead-out area, andwhere data is written in and/or read from, and that describes datawobbles that are recorded before writing of data in the data area. Thelead-in area includes a read-only area for only reading having a firstwobble, a readable/writable area having a second wobble that isdifferent from the first wobble, and a connection area positionedbetween the read-only area and the readable/writable area.

To achieve the above and other objects, there is provided an opticaldisc including a read-only area for only reading having a first wobblehaving a high frequency, an end-marking area disposed next to theread-only area area and containing data representing an end of theread-only area for only reading, a connection area disposed next to theend marking area, and a readable/writable area having a second wobblewhose frequency is lower than the high frequency of the first wobble.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention willbecome more apparent and more readily appreciated from the followingdescription of the preferred embodiments, taken in conjunction with theaccompanying drawings of which:

FIGS. 1 and 2 are views of general optical discs each having aconnection zone;

FIG. 3 is a view of a DVD-RAM having the connecting zone in the opticaldisc system of FIG. 2;

FIG. 4 is a view of another example of the connection zone of theoptical disc of FIG. 2;

FIGS. 5A through 5C and 6 are an optical disc according to embodimentsof the present invention;

FIG. 7 is a block diagram of a data structure of the optical disc ofFIGS. 5A through 6;

FIG. 8 is a graph illustrating relationships among the number of wobblesper bit, frequency of the wobbles, and track pitches of the wobbles inrecorded wobble data of the optical disc of FIGS. 5A through 6;

FIG. 9 is a view explaining a relationship between a first physicaladdress of a read-only area for only reading and a second physicaladdress of a readable/writable area in the optical disc of FIGS. 5Athrough 6;

FIGS. 10 and 11 are views each explaining a header field in a read-onlyarea in the optical disc of FIGS. 5A through 6;

FIG. 12 is a view of another data structure of the optical discaccording to another embodiment of the present invention; and

FIG. 13 is a schematic view of an optical disc recording/reproducingsystem according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the present invention, examples of which are illustratedin the accompanying drawings, wherein like reference numerals refer tothe like elements throughout. The embodiments are described in order toexplain the present invention by referring to the figures.

A recording medium, e.g., a disc or an optical disc, according to anembodiment of the present invention is a recording/reproducing disc thatincludes a read-only area 10 for only reading, a readable/writable area30, and a connection area 20 disposed between the readable/writable area30 and the read-only area 10. Read-only data for only reading, which iswritten as information regarding the optical disc or recordingparameters in the read-only area 10, is recorded as a predeterminedfirst wobble not to be deleted arbitrarily by a user, and data writtenin the readable/writable area 30 is recorded as a second wobble which isdifferent from the first wobble. Here, the data written in thereadable/writable area 30 may be data for a disc test or a drive test,for example.

The first and second wobbles may be embodied variously if the first andsecond wobbles are different from each other. For instance, as shown inFIG. 5A, the first wobble and second wobbles may be in a form of asaw-toothed wobble 12 and a waved low-frequency wobble 32, respectively.A third wobble of the connection area 20 may be a low-frequency wobble22 having the same form as the waved low-frequency wobble 32 of thesecond wobble.

Also, as shown in FIG. 5B, the first wobble may be a high-frequencywobble 14 having a high frequency, and the second wobble may be alow-frequency wobble 34 whose frequency is lower than the high frequencyof the first wobble 14. The third wobble in the connection area 20 maybe a high-frequency wobble 24 having the same frequency as thehigh-frequency wobble 14 of the first wobble. Otherwise, the firstwobble in the read-only area 10 may have the high frequency, the secondwobble in the readable/writable area 30 may have the low frequency, andthe third wobble in the connection area 20 may have the same frequencyas the second wobble in the readable/writable area 30.

As shown in FIG. 5C, the first wobble in the read-only area 10 may havethe high-frequency wobble 14, the second wobble in the readable/writablearea 30 may have the low-frequency wobble, and the third wobble of theconnection area 20 may be a mirror area.

Otherwise, as shown in FIG. 6, the first wobble may have thehigh-frequency wobble 14 having the high frequency, the second wobblemay have the low-frequency wobble 34 having the low frequency, and thethird wobble in the connection area 20 may be a wobble 26 whosefrequency gradually decreases so that the entire frequency can besmoothly reduced from the high frequency of the first wobble 14 to thelow frequency of the second wobble 34. As a result, a transition timeappears between the high frequency of the high-frequency wobble 14 inthe read-only area 10 and the low frequency of the low-frequency wobble34 in the readable/writable area 30, thereby increasing a reliability ofa read/write signal of a reproducing apparatus, e.g., an opticalapparatus, reading/writing the read/write signal from/on the opticaldisc. In this case, a frequency of a phase locked loop (PLL) of theoptical apparatus can be stabilized while reducing a secondhigh-frequency distortion component contained in the low frequency.

Especially, as shown in FIGS. 5A through 6, when the first wobble 12, 14in the read-only area 10 has the high frequency and the second wobble32, 34 in the readable/writable area 30 has the low frequency, it ispossible that the frequency of the high-frequency wobble (first wobble)12, 14 is a positive multiple of that of the low-frequency wobble(second wobble) 32, 34. That is, provided that the frequency of thehigh-frequency wobble is f_(HF) and the frequency of the low-frequencywobble is f_(LF), the following equation (1) is obtained:ƒ_(HF)=nƒ_(LF) (n is a positive integer) . . . (1)

As expressed in equation (1), the frequency of the high-frequency wobbleis a positive multiple of that of the high-frequency wobble, thus makingwobbles in the read-only area 10 and the readable/writable area 30 to bein phase. This embodiment describes a case where the first wobble 12 or14 is different from the second wobble 32 or 34, respectively, in termsof frequency. These first and second wobbles can be different from eachother in terms of amplitude or phase as well.

Meanwhile, as shown in FIG. 7, a data structure of a DVD is defined, forexample, by a lead-in area that contains the read-only data written inan inner portion of the optical disk, a user data area containing userdata, and a lead-out area disposed in an outer portion of the opticaldisk. If the present invention is applied to such a DVD, the lead-inarea includes the read-only area 10 in which the read-only data iswritten as the first wobble 12 or 14, the readable/writable area 30 inwhich the second wobble 32 or 34, which has different forms from thefirst wobble 12 or 14, is formed, and the connection area 20 disposedbetween the read-only area 10 and the readable/writable area 30.

FIG. 8 is a graph illustrating relationships among the number ofwobbles, a frequency of the wobbles and track pitches of the wobbleswhich are required per bit of wobble data if the first wobble is thesaw-toothed wobble 12. Here, a radius of the read-only area 10 is fromabout 22.3 mm to 23.1 mm, the track pitch is from about 0.30 μm to 0.34μm, and the number of wobbles in the read-only area 10 is from 10 to 40in groups of five wobbles. Each of tracks formed in the read-only area10, the connection area 20, and the readable/writable area 30 has thesame track pitch. For instance, if the number of wobbles per bit of thewobble data is set to be thirty five when a track pitch is 0.32 μm, thefrequency of the wobble is 7.5 MHz in the read-only area 10, which isvery high frequency in consideration of a fact that the frequency of thewobble generated by a general DVD is less than 1 MHz. The frequency ofthe wobble can be variously set by controlling the track pitch and thenumber of the wobble per bit of the wobble data.

For continuity of an address, it is possible that a first physicaladdress of the readable/writable area 30 is disposed next to a lastphysical address of the read-only area 10. As shown in FIG. 9, if thelast physical address of the read-only area 10 is m, the first physicaladdress of the readable/writable area 30 must be m+1.

In general, a signal obtained from the wobble during writing/readingoperations is used as a reference clock signal during a writingoperation. However, the optical disc according to the present inventionrequires an additional clock signal to obtain a data signal from thefirst wobble 12 or 14, because the first wobble 12 or 14 of theread-only data is the high-frequency wobble and the second wobble 32 or34 in the readable/writable area 30 is the low-frequency wobbledifferent from the first wobble 12 or 14. In other words, the referenceclock signal in the read-only area 10 is different from a wobble clocksignal in the readable/writable area 30. Therefore, the reference clocksignal generated by a drive system is used to read the wobble of theread-only data, but another reference clock signal for the low-frequencywobble of the readable/writable area 30 is generated from the wobbles ofthe read-only data in the read-only area 10.

If an address, which represents a position in the optical disc, iswritten as the wobble on the groove, the address may be repeatedlywritten to all basic minimum write units, and data may be writtenaccording to a modulation mode determined by the groove in thereadable/writable area 30. Meanwhile, in an event that the read-onlydata is written as the first wobble 14, which is the high-frequencywobble, in the read-only area 10, the read-only area 10 may be definedby a header field that contains address data, and a data fieldcontaining the read-only data written as the high-frequency wobble onthe groove, as shown in FIG. 10. The header field may include a physicaladdress (PID) area that is expressed in basic minimum write units suchas a sector, and a variable frequency oscillator (VFO) area containinginformation having a specific pattern for stably operating the phaselocked loop (PLL) of a reproducing circuit of the reproducing apparatus.The header field may be disposed at a head or end portion of errorcorrection code (ECC) write units disposed in the read-only area 10 oras an interface between the ECC write units.

The address data written in the header field of the read-only area 10 isvery important data which must be necessarily read before reading otherwritten data. If the address data has a higher frequency than that ofthe second wobble in the readable/writable area 30, a signal read fromthe first wobble, which contains the address data, becomes smaller thananother signal read from other written data in the readable/writablearea 30 or the user data in the user data area of FIG. 7. If the signalof the address data is small, this decreases an address detectioncapability of the optical disc, thus lowering the reliability of thereading/writing operations of the reproducing apparatus. To solve thisproblem, as shown in FIG. 11, the header field uses the same lowfrequency as the second wobble 32 or 34 used in the readable/writablearea 30, and the data field for only reading uses the high-frequencywobble. As a result, the address data can be uniformly detectedthroughout the optical disc, and thus the reading/writing capability ofthe optical disc can be enhanced.

As can be seen from FIG. 12, another optical disc according to anotherembodiment of the present invention may further include an end-markingarea 45 that provides a drive (not shown) with data and that aconnection area 50 and a readable/writable area 55 follow a read-onlyarea 40 having the high frequency. The end-marking area 45 is formed ofwobbles that are different from the wobbles in the read-only area 40.For instance, a wobble in the end-marking area 45 is different from thatin the read-only area 40 in terms of at least one of frequency, phase,period and amplitude.

FIG. 13 is a schematic view of an optical disc recording/reproducingsystem according to another embodiment of the present invention. Thissystem includes a read/write signal processor 110, a servo controller115, and an optical pickup 130 that is used to read data from a disc153. The optical pickup 130 includes an optical source 140 that suppliesa laser beam (light), a collimating lens 142 that collimates the laserbeam output from the optical source 140, a beam splitter 144 thatchanges a path of the laser beam, and an objective lens 146 that focusesthe laser beam, which passes through the beam splitter 144, on a portionof the disc 153. The read/write signal processor 110 includes aphotodetector 148 that receives the laser beam reflected from the disc153, an operational circuit unit 150 that processes an electric signaloutput from the photodetector 148, a user data detector 113 that detectsa radio-frequency (RF) signal out of signals output from the operationalcircuit unit 150, via a first channel Ch1, and a wobble signal detector114 that detects a tracking error signal and a wobble signal, via asecond channel Ch2.

In conclusion, the optical disc according to the present inventionincludes the connection area 20 and the end-marking area 45 thusincreasing the reading/writing operations. Further, it is possible tomore stably and completely perform a reading/writing performance on theoptical disc using the optical disc recording/reproducing system.

As described above, according to the present invention, the optical discincludes the grooves, the first wobbles in the read-only area, which aredifferently formed from the second wobbles in the readable/writablearea, and the connection area formed between the read-only area and thereadable/writable area. In particular, the connection area can preventthe occurrence of a crosstalk between two areas having differentwobbles. Accordingly, the reading/writing operations can be stably andcompletely performed throughout the entire optical disc.

Although a few preferred embodiments of the present invention have beenshown and described, it would be appreciated by those skilled in the artthat changes may be made in this embodiment without departing from theprinciples and sprit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A reproducing system compatible with an optical disc in which data iswritten on and/or read from, the optical disc including a read-onlyarea, having a first wobble, in a lead-in area of the optical disc, areadable/writable area having a second wobble that is different from thefirst wobble, with the readable/writable area comprising a plurality ofcontiguous minimum write units, and a connection area formed between theread-only area and the readable/writable area, the system comprising: anoptical pickup unit to read a first wobble of the read-only area of theoptical disc and a second wobble of the readable/writable area of theoptical disc; and a processor to control a reproducing of at least theread-only area of the optical disc, and to control a reproducing of atleast the readable/writable area of the optical disc, with thecharacteristic of the first wobble of the read-only area and thecharacteristic of the second wobble of the readable/writable area beingdifferent.
 2. The system of claim 1, wherein, in the optical disc, thefirst wobble has a high frequency as the characteristic of the firstwobble, and the second wobble has a low frequency lower than that of thefirst wobble as the characteristic of the second wobble.
 3. The systemof claim 2, wherein, in the optical disc, the connection area comprisesa mirror area.
 4. A reproducing system compatible with an optical discin which data is written on and/or read from, the optical disc includinga read-only area having a first wobble, a readable/writable area havinga second wobble that is different from the first wobble, with thereadable/writable area comprising a plurality of contiguous minimumwrite units, and a connection area formed between the read-only area andthe readable/writable area, wherein the first wobble has a highfrequency, and the second wobble has a low frequency lower than that ofthe first wobble, and wherein the read-only area comprises a headerfield containing first address data, and the readable/writable areacomprises a wobbled groove containing second address data, the systemcomprising: an optical pickup unit to read a first wobble of theread-only area of the optical disc and a second wobble of thereadable/writable area of the optical disc; and a processor to control areproducing of at least the read-only area of the optical disc basedupon a first reference clock generated at least based upon acharacteristic of the first wobble of the read-only area, and to controla reproducing of at least the readable/writable area of the optical discbased upon a second reference clock generated at least based upon acharacteristic of the second wobble of the readable/writable area, withthe characteristic of the first wobble of the read-only area and thecharacteristic of the second wobble of the readable/writable area beingdifferent.
 5. The system of claim 4, wherein the optical disc furthercomprises: error correction code (ECC) write units, wherein the headerfield is disposed at a beginning or end portion of the ECC write units,or at a border between the ECC write units.
 6. The system of claim 5,wherein, in the optical disc, the header field comprises a wobble havingthe same low frequency as the second wobble in the readable/writablearea.
 7. The system of claim 6, wherein the optical disc furthercomprises a recording layer having the read-only area, thereadable/writable area, and the connection area.
 8. The system of claim2, wherein, in the optical disc, the high frequency of the first wobbleis expressed as a function of the low frequency of the second wobble byƒ_(HF)=nƒ_(LF), where n is a positive integer, and f_(HF) and f_(LF)denote the high and low frequencies of the first wobble and the secondwobble, respectively.
 9. The system of claim 1, wherein, in the opticaldisc, the first wobble comprises a saw-toothed wobble.
 10. The system ofclaim 1, wherein, in the optical disc, the connection area comprises amirror area.
 11. A reproducing system compatible with an optical disc inwhich data is written on and/or read from, the optical disc including aread-only area having a first wobble, a readable/writable area having asecond wobble that is different from the first wobble, with thereadable/writable area comprising a plurality of contiguous minimumwrite units, and a connection area formed between the read-only area andthe readable/writable area, and, wherein the read-only area comprises aheader field containing first address data, and the readable/writablearea includes wobbled grooves containing second address data, the systemcomprising: an optical pickup unit to read a first wobble of theread-only area of the optical disc and a second wobble of thereadable/writable area of the optical disc; and a processor to control areproducing of at least the read-only area of the optical disc basedupon a first reference clock generated at least based upon acharacteristic of the first wobble of the read-only area, and to controla reproducing of at least the readable/writable area of the optical discbased upon a second reference clock generated at least based upon acharacteristic of the second wobble of the readable/writable area, withthe characteristic of the first wobble of the read-only area and thecharacteristic of the second wobble of the readable/writable area beingdifferent.
 12. The system of claim 11, wherein the optical disc furthercomprises error correction code (ECC) write units, wherein the headerfield is disposed at a beginning or end portion of the ECC write units,or at a border between the ECC write units.
 13. The system of claim 12,wherein, in the optical disc, the header field comprises a wobble havingthe same low frequency as that of the second wobble in thereadable/writable area.
 14. A reproducing system compatible with anoptical disc including a read-only area, having a first wobble having ahigh frequency, in a lead-in area of the optical disc, an end-markingarea disposed next to the read-only area and containing datarepresenting an end of the read-only area, a connection area disposednext to the end marking area, and a readable/writable area disposed nextto the connection area and having a second wobble whose frequency islower than that of the first wobble, with the readable/writable areacomprising a plurality of contiguous minimum write units, the systemcomprising: an optical pickup unit to read a first wobble of theread-only area of the optical disc and a second wobble of thereadable/writable area of the optical disc; and a processor to control areproducing of at least the read-only area of the optical disc basedupon a first reference clock generated at least based upon acharacteristic of the first wobble of the read-only area, and to controla reproducing of at least the readable/writable area of the optical discbased upon a second reference clock generated at least based upon acharacteristic of the second wobble of the readable/writable area, withthe characteristic of the first wobble of the read-only area and thecharacteristic of the second wobble of the readable/writable area beingdifferent.
 15. The system of claim 14, wherein, in the optical disc, thehigh frequency of the first wobble is expressed as a function of the lowfrequency of the second wobble byƒ_(HF)=nƒ_(LF), where n is an integer, and f_(HF) and f_(LF) denote thehigh frequency of the first wobble and the low frequency of the secondwobble, respectively.
 16. The system of claim 14, wherein, in theoptical disc, the connection area comprises a mirror area.
 17. Areproducing system compatible with an optical disc in which data iswritten on and/or read from, the optical disc including a read-only areahaving a first wobble, a readable/writable area having a second wobblethat is different from the first wobble, and a connection area formedbetween the read-only area and the readable/writable area, with theconnection area comprising at least a track, the system comprising: anoptical pickup unit to read a first wobble of the read-only area of theoptical disc and a second wobble of the readable/writable area of theoptical disc; and a processor to control a reproducing of at least theread-only area of the optical disc based upon a first reference clockgenerated at least based upon a characteristic of the first wobble ofthe read-only area, and to control a reproducing of at least thereadable/writable area of the optical disc based upon a second referenceclock generated at least based upon a characteristic of the secondwobble of the readable/writable area, with the characteristic of thefirst wobble of the read-only area and the characteristic of the secondwobble of the readable/writable area being different.
 18. The system ofclaim 17, wherein, in the optical disc, the first wobble has a highfrequency, and the second wobble has a low frequency lower than that ofthe first wobble.
 19. A reproducing system compatible with an opticaldisc including a read-only area having a first wobble having a highfrequency, an end-marking area disposed next to the read-only area andcontaining data representing an end of the read-only area, a connectionarea disposed next to the end marking area, with the connection areacomprising at least a track, and a readable/writable area disposed nextto the connection area and having a second wobble whose frequency islower than that of the first wobble, the system comprising: an opticalpickup unit to read a first wobble of the read-only area of the opticaldisc and a second wobble of the readable/writable area of the opticaldisc; and a processor to control a reproducing of at least the read-onlyarea of the optical disc based upon a first reference clock generated atleast based upon a characteristic of the first wobble of the read-onlyarea, and to control a reproducing of at least the readable/writablearea of the optical disc based upon a second reference clock generatedat least based upon a characteristic of the second wobble of thereadable/writable area, with the characteristic of the first wobble ofthe read-only area and the characteristic of the second wobble of thereadable/writable area being different.
 20. A reproducing systemcompatible with an optical disc in which data is written on and/or readfrom, the optical disc including a read-only area, having a firstwobble, in a lead-in area of the optical disc, in a lead-in area of theoptical disc, a readable/writable area having a second wobble that isdifferent from the first wobble, with the readable/writable areacomprising a plurality of contiguous minimum write units, and an areaformed between the read-only area and the readable/writable area, thesystem comprising: an optical pickup unit to read a first wobble of theread-only area of the optical disc and a second wobble of thereadable/writable area of the optical disc; and a processor to control areproducing of at least the read-only area of the optical disc basedupon a first reference clock generated at least based upon acharacteristic of the first wobble of the read-only area, and to controla reproducing of at least the readable/writable area of the optical discbased upon a second reference clock generated at least based upon acharacteristic of the second wobble of the readable/writable area, withthe characteristic of the first wobble of the read-only area and thecharacteristic of the second wobble of the readable/writable area beingdifferent.
 21. The system of claim 20, wherein, in the optical disc, thefirst wobble has a high frequency, and the second wobble has a lowfrequency lower than that of the first wobble.
 22. A reproducing systemcompatible with an optical disc including a read-only area, having afirst wobble having a high frequency, in a lead-in area of the opticaldisc, an end-marking area disposed next to the read-only area andcontaining data representing an end of the read-only area, an areadisposed next to the end marking area, and a readable/writable areadisposed next to the area and having a second wobble whose frequency islower than that of the first wobble, with the readable/writable areacomprising a plurality of contiguous minimum write units, the systemcomprising: an optical pickup unit to read a first wobble of theread-only area of the optical disc and a second wobble of thereadable/writable area of the optical disc; and a processor to control areproducing of at least the read-only area of the optical disc basedupon a first reference clock generated at least based upon acharacteristic of the first wobble of the read-only area, and to controla reproducing of at least the readable/writable area of the optical discbased upon a second reference clock generated at least based upon acharacteristic of the second wobble of the readable/writable area, withthe characteristic of the first wobble of the read-only area and thecharacteristic of the second wobble of the readable/writable area beingdifferent.